This guide lists lighting levels of accepted standards and luminaire placement for common parking garage layouts.
There are reference links and a few handy tools near the end. Table-1 shows illuminance figures in IESNA, the NPA and DOE/GSA for given areas of a parking garage.
Table 1
*Facing the drive aisle 5' above the parking surface at points of lowest horizontal illuminance. (LM-64-01) Bold text & yellow-background are areas that can be achieved with properly designed LED luminaires. Red text & orange-background represents a problem area for common downlight fixtures. IESNA has a measurement guide specifically for parking garage lighting: LM-64-01 gives results similar to RP-20-98. The LM-64 standard may be difficult to understand without first understanding RP-20. Up-light is not required in either RP-20-98 or NPA parking garage Standard, however, it improves ambiance in most enclosed structures. Vertical footcandles are specified in RP-20 and LM-64. A properly designed LED parking garage light will provide illumination for vertical walls with less waste and glare in other areas. Some LED luminaires not specifically designed for parking garage lighting are being tried in this application, and some rely upon floor reflectivity to achieve the required vertical footcandles. Downlights that rely upon floor reflectivity may conveniently meet the LM-64 criteria since that suggests measurements during periods of minimal vehicle occupancy. In this case, vertical footcandle levels will be diminished during garage activity, which is precisely when the vertical illuminance is most necessary. A careful review of vertical illuminance is essential without relying upon an empty garage floor.  
Cutoff is essential on the motorist approach side to prevent blinding the driver.
The luminaire should be available with cutoff specified, or it should be field adjustable.
The required cutoff angle will depend on the application and mounting height. | ||||||||||||||||||||||||||||||||
| Standardized Parking Stall Layout | ||
Conceptually we may consider a Parking Module as six parking stalls within an area approximately
28-ft. x 60-ft. This helps us define and organize the space, and predict the lighting requirements.
There are multiples of these modules, end to end, or side to side. Beam spacing is typically 18 to 22 ft. |
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But parking modules don't always fit according to the beams, and the structure may have only eight feet of clearance.
The larger luminaires must sometimes fit between beams.
Lighting manufacturers have provided for two commonly known lighting layouts: "single row" and "double row" designs. Of course variations arise because every floor plan has its unique drive aisles and turns, signage locations, corners, windows and stall walls. |
| Standardized Lighting Layout | |||
Single row lighting is illustrated below for an enclosed structure.
Luminaires are centered above each drive aisle to light the far walls of parking modules. Each luminaire has cutoff (the curved-in shape) toward the driver approach to reduce disability glare.
The lighting layout for this floor plan uses eight luminaires.
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Double row lighting is illustrated below for an enclosed structure. Two rows of luminaires are shown with a row along each side of the drive aisle.
These luminaires are ordinarily similar to the single row style but rotated 90°. The lighting layout for this floor plan uses eight luminaires.
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Reflectance adds to the room illumination, and is a function of surface condition. White light against a smooth gray surface will reflect approximately 50%. In commercial settings with white light, wall reflectance is often estimated at 50%, ceilings 80% and floors 20%, or, that's the amount we use in calculations.
Smooth gray concrete walls can naturally have a 50% reflectance value. White paint on ceilings will easily boost those to 80% reflectance. Ceilings should always be painted if possible. Floor reflectance is typically low, and using that in calculations is misleading because a full garage will have most of the floor covered with vehicles. Its light enhancing benefit will change with garage activity and maintenance. Walls and ceilings usually contribute to better lighting as they enhance and smooth the total room illumination.
Clean, reflective surfaces can improve the overall Average to Minimum Illumination Ratio, and when surface treatment and painting is designed in from the project start, more energy can be saved. Proper painting of the walls can boost reflectance by over 20%, and could allow reduction by that much in energy usage with no reduction in illumination quality.
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Visit IESNA for RP-20-98 & LM-64-01 and visit National Parking Association for Standards.
Download the DOE/GSA Specification. The lighting system design must account for each interior surface having either light reflectivity or light absorption. When a surface isn't present, that border must be considered an opening through which light will escape. Open areas or windows require cutoff luminaires to avoid waste and avoid sending light pollution elsewhere. Given the vertical illumination that standards suggest, light energy can go right out the window. Outward-facing luminaires must have sharp downward cutoff, or, they must be wall mounted and shine back into the area. Windows or open back-to-back parking bays require more attention to layout.
Painting of interior surfaces is not essential, however, this Program is about conserving energy. Some manufacturer's paint and surface treatments not only boost reflectance, they repel typical garage dirt and hydrocarbon buildup to maintain that reflectance over long periods of time.
The low profile allows LED luminaires to mount either on the beams or suspend between the beams, when HID and Induction luminaires are too bulky.